In many industrial applications relatively movable parts may closely approach one another or make undesirable contact in inaccessible places where direct observation is not possible. Still it is desirable to determine whether and where such contact or small clearances occur so that suitable adjustments may be made to the apparatus or process. Detection of a small clearance between parts is important in preventing contact since in many cases additional wear of an apparatus may lead to actual contact. It is thus advantageous to inexpensively measure the clearance between parts at one or several locations.
One example of where clearance measurement is necessary is in the testing of circuit boards carrying electrical components. Test probes engage one side of the circuit board while a fixture presses against the other side. If not properly adjusted, the fixture may bear against components or a force unbalance may flex the board, causing damage. Measuring the clearance will allow determination of whether fixture adjustment or redesign is necessary.